How Low Can You Go? Nanoscale Membranes for Efficient Water Electrolysis

Motivated by the need to lower the cost of hydrogen (H2) production by water electrolysis, significant research efforts are focused on making proton (H+) exchange membrane (PEM) water electrolyzers more efficient and capable of operating at higher current densities. These aims can be met by making H+-conducting membranes thinner, which has the effect of lowering ohmic drops across the membrane that represent the largest efficiency loss at high current densities (>2 A cm–2). However, decreasing membrane thickness below 50 μm is not trivial due to trade-offs between membrane resistance, H2 crossover (safety), membrane degradation, and manufacturing throughput. Herein, descriptions of key processes, limitations, and trade-offs that arise in thin membranes are provided that can be used to guide the design of ultrathin (i.e., submicron thick), low-resistance membrane materials that have the potential to transform the field of clean H2 production.